1. Field of the Invention
The present invention relates to a fastener element for a concealed type slide fastener in which coupled elements are not seen from a tape surface when the fastener elements (hereinafter, sometimes abbreviated as just element) attached along a side edge of each of a pair of fastener tapes are coupled with each other, and to a concealed type slide fastener in which the same elements are arranged in line on element attaching edge portions of the fastener tapes.
2. Description of the Related Art
Conventionally, fastener elements (hereinafter sometimes abbreviated as just element) for using in this kind of concealed type slide fastener are mounted along element attaching edge portions each including a core thread portion at a side edge of a fastener tape by injection molding of synthetic resin or die-casting of zinc alloy or the like.
The element for using in this concealed type slide fastener has a substantially U shaped axial section, and is mounted such that a coupling portion of the element is directed toward the inside of the fastener tape. Alternatively, a concealed type slide fastener is constituted by inserting a slider into an element row in a state, in which the element attaching edges of the fastener tape attached with the elements are folded back into a letter U shape.
However, if a pulling stress is applied to such a concealed type slide fastener in a tape width direction from both sides of the fastener tape when the elements are coupled with each other, a gap is generated between right and left fastener tapes so that coupled elements are seen from the tape surface, thereby not securing concealed property. Further, there is another problem that since the sliding operation of the slider is heavy, it makes difficult to operate the slider smoothly when the concealed type slide fastener is opened/closed.
To solve the above-described problem, for example, Japanese Utility Model Publication No. 52-10483 has disclosed a concealed type slide fastener element having the following configuration. That is, a coupling portion is provided on one end of a tape fixing portion of an element having a U shaped section such that shape of the upper and lower portions of the coupling portion are symmetrically different, and symmetrical engaging faces in the right and left direction are formed on a border between the upper and lower portions, while a projecting portion is provided projectingly on the other end of the tape fixing portion.
The concealed type slide fastener provided with the elements described in the Japanese Utility Model Publication No. 52-10483 can ensure a stable coupled state without any displacement because the vertical motion of the element is blocked by the engaging face when right and left elements are coupled by sliding the slider. As a consequence, the element can be prevented from rotating even if a tension is applied in the tape width direction so as to block generation of a gap between the right and left fastener tapes.
According to the Japanese Utility Model Publication No. 52-10483, a gap is generated between the fixing portion of the element and the fastener tape by providing the projecting portion on the other end of the tape fixing portion, thereby making it possible to allow the slider to slide lightly and prevent the tape from being damaged.
The Japanese Utility Model Publication No. 2598345 has disclosed the following concealed type slide fastener element. That is, the element described in the Japanese Utility Model Publication No. 2598345 is an element having a substantially U shaped axial section in which a tape mounting groove is formed. Upper and lower portions of a coupling portion located at one end have different shapes while an engaging face is formed on a border between the both. A vertical wall face is formed at the front end of the upper portion, and the thickness of the lower portion is set to be half of that of the element main body. Further, the tape mounting groove is formed obliquely, and a connecting portion for connecting one end side of the element with the other end side is provided on part of the tape mounting groove. Moreover, a slider guide piece is provided projectingly at the front end of the other end of the element to improve the sliding performance of the slider.
The Japanese Utility Model Publication No. 2598345 has described an effect that the right and left elements can be coupled securely and a vertical displacement can be restricted sufficiently by using such an element in the concealed type slide fastener. In addition, the document has described that if a fastener chain is bent to the fastener tape side in the longitudinal direction, it can be bent very easily without being stiffened like the conventional product.
Furthermore, the Japanese Utility Model Publication No. 2598345 has said that horizontal pulling force and coupling strength of the slide fastener can be raised because the tape mounting groove is formed obliquely and the coupling portion is provided in part thereof, and that the other end portion of the element can be formed thinly so as to finish the element itself into a thin and beautiful configuration.
In recent years, the concealed type slide fastener has been widely applied to a variety of products such as clothes or automobile passenger seat covers by taking an advantage that the slide fastener does not lower the design performance of such a product because it has concealed property which conceals elements. For this reason, the concealed type slide fastener has been demanded to have a high performance which is capable of securing the concealed property and coupling strength even if the slide fastener is used under various environments or conditions.
More specifically, when the concealed type slide fastener is applied to the seat cover of automobile or the like, a pulling stress which pulls fastener stringers from both sides is applied to the concealed type slide fastener when the fastener elements are going to be coupled with each other or the slide fastener is in a coupled state, because the seat cover is formed in a smaller size than the external dimensions of a cushion body. However, when the strong pulling stress is applied to the concealed type slide fastener attached with the conventional elements as described in the Japanese Utility Model Publication No. 52-10483 and the Japanese Utility Model Publication No. 2598345, there likely occurs such a fault as generation of a gap between the right and left fastener tapes, and release of coupling of elements.
Further, such a conventional concealed type slide fastener is weak against a twisting force or a pushing force. For example, if the concealed type slide fastener sewed on clothes receives a twisting force or a pushing force, coupling portions of the elements are easy to be deformed or damaged so that the slide fastener cannot bear a long term use.
In the element of the Japanese Utility Model Publication No. 52-10483, both the upper and lower portions of the coupling portion are formed up to the front ends. When right and left elements are coupled, the side ends of the upper and lower portions of the coupling portion of one element are fitted to the side ends of the upper and lower portions of an adjoining coupling portion. As a consequence, when bending the fastener chain, its bending operation cannot be carried out smoothly because the fastener chain has stiffness and is lack of plasticity.
On the other hand, although the element of the Japanese Utility Model Publication No. 2598345 can be bent easily as described above, the coupling head and neck portion are easy to be deformed or damaged because the coupling head is provided protrudedly from the base portion (main body) of the element through a constricted neck portion.
The present invention has been achieved in views of the above-described problems, and an object of the invention is to provide a fastener element for a concealed type slide fastener, having an excellent concealed property and coupling strength and capable of preventing generation of a gap between right and left fastener tapes even if pulling stress is received and generation of deformation and damage even if twisting force or pushing force is received, and to provide a concealed type slide fastener equipped with the fastener elements.